1. Field of the Invention
The present invention relates to a method for evaluating the quality of culture of pluripotent stem cells.
2. Description of the Related Art
Pluripotent stem cells which can differentiate into various tissues are drawing an increasing attention in the fields of medicine and bioscience including regenerative medicines and drug discovery for instance. To use pluripotent stem cells for the purpose of research, treatments, etc., it is necessary to increase the number of the cells without damaging the pluripotency of the cells and culture for this purpose is called “maintenance culture.” Pluripotent stem cells may however for some reason lose their pluripotency and differentiate into cells which have only a particular function while being cultured and maintained. Therefore, further research is in progress to find a culture condition under which a pluripotent stem cell can be stably cultured while still retaining its pluripotency.
The cell evaluation technique described in JP2011-229409A for example is one of methods proposed for evaluating the state of cultured pluripotent stem cells. According to this technique, the state of differentiation of pluripotent stem cells is evaluated based upon the feature value morphology of cell colonies included in captured images of cultured pluripotent stem cells.
According to the conventional technique above, in a condition that a plurality of cells are cocultured, the cells are evaluated based on how the feature value of a colony which needs to be evaluated is related to the feature values of cells around the colony. Specifically describing this, through image analysis of a captured image of a sample, colonized portions of cells are extracted, and in accordance with the calculated feature values of the images of the colonized portions and the surrounding areas, the state of the cell colonies is evaluated.
Meanwhile, for the purpose of judging whether a culture condition is favorable or poor, rather than detailed information regarding each colony, the state of culture of a sample as a whole needs to be comprehensively understood. To this end, more direct evaluation utilizing a characteristic which can be seen from an image is more desirable than relative evaluation which involves comparison of extracted characteristics of multiple sections within the image with each other. However, no such evaluation method has been established up to today. Evaluation has so far been subjective and dependent upon visual observation by an operator, inevitably leading to varied evaluation results. This has given rise to the need for an established technique for objective and simple evaluation of the quality of a cultured sample.